1. Field of the Invention
The present invention relates to an image brightness adjusting method, an object tracking method and an object tracking apparatus, and particularly relates to an image brightness adjusting method, an object tracking method and an object tracking apparatus which compensate brightness of other pixels according to a difference between brightness information of at least one pixel and background brightness information.
2. Description of the Prior Art
FIG. 1 is a schematic illustrating a situation that an object generates a dark region while utilizing a conventional object tracking apparatus. As shown in FIG. 1, the object tracking apparatus 100 comprises a touch control panel 101, an image detecting apparatus 102, light guiding bars 105, 109 and light emitting diodes 103, 107, 111, 113. Light guiding bars 105, 109 are provided at two sides of the touch control panel 101. The light emitting diodes 103, 107, 111, 113 are respectively provided at ends of the light guiding bars 105, 109, to emit light to the touch control panel 101 via light guiding bars 105, 109. The image detecting apparatus 102 is provided opposite to the light guiding bars 105, 109. The image detecting apparatus 102 can detect a projected image of the object Ob (ex. a user's finger) if the object Ob moves on the touch control panel 101. Such projected image is a dark region generated by covering light from the light guiding bars 105, 109 with the object Ob. By this way, a location for the object Ob can be acquired. In FIG. 1, the dark region curve DC indicates a brightness information curve formed by the dark region (ex. an average brightness for a plurality of pixel images). The object tracking apparatus 100 can compute a location or a centroid of the object according to such dark region curve DC. Please note a value for each point of the dark region curve DC corresponds to at least one brightness value for each pixel line of an image from the object Ob, which is caught by the image detecting apparatus 102. For example, a sum or an average for brightness of a plurality of pixels can be applied as values for corresponding points of the dark region curve DC. Take the X point on the dark region curve DC in FIG. 1 for example, the brightness information for the X point can be a sum or an average for brightness of pixels in the X-th line image detecting apparatus 102. The background information curve BG indicates the background brightness information detected by the image detecting apparatus 102 (ex. an average of background brightness). The background information curve BG can be acquired via the steps of acquiring the dark region curve DC. Take the Y point on the background information curve BG in FIG. 1 for example, the brightness information for the Y point can be a sum or an average for brightness of pixels in the Y-th line of the image detecting apparatus 102.
FIG. 2 is a schematic illustrating a situation that a plurality of objects generate a dark region while utilizing a conventional objects tracking apparatus. As shown in FIG. 2, if two objects such as two fingers touch the touch control panel 101 simultaneously (or a distance between the objects and the touch control panel 101 is smaller than a predetermined value), two separate dark regions DC_1, DC_2 are supposed to be formed. Practically, however, if two objects are too close, adjacent pixels will affect each other, thus a mixed dark region curve DC_M as shown in FIG. 2 is generated. In such case, if the object tracking apparatus 100 directly computes locations or centroids for the objects Ob_1 and Ob_2 according to the mixed dark region curve DC_M, the locations or centroids may be wrongly computed, such that the accuracy for tracking the object will be affected.